science
- Created by: liberty cook
- Created on: 10-05-15 10:56
life processes
Life processes
Living organisms have certain life processes in common. There are seven things that they need to do to count as being alive. The phrase MRS GREN is one way to remember them:
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Movement - all living things move, even plants
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Respiration - getting energy from food
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Sensitivity - detecting changes in the surroundings
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Growth - all living things grow
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Reproduction - making more living things of the same type
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Excretion - getting rid of waste
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Nutrition - taking in and using food
life processes
It can be easy to tell if something is living or not. A teddy bear might look like a bear, but it cannot do any of the seven things it needs to be able to do to count as being alive.
A car can move, it gets energy from petrol (like nutrition and respiration), it might have a car alarm (sensitivity), and it gets rid of waste gases through its exhaust pipe (excretion). But it cannot grow or make baby cars. So a car is not alive.
cells
organisms are made up of cells .
cells
Animal cells and plant cells both contain:
Plant cells also contain these parts, which are not found in animal cells:
cells
Cells and their functions
Humans are multicellular. That means we are made of lots of cells, not just one cell. The cells in many multicellular animals and plants arespecialised, so that they can share out the processes of life. They work together like a team to support the different processes in an organism.
Cells, tissues, organs and systems
Cells, tissues, organs and systems
Multicellular organisms are organised into increasingly complex parts. In order, from least complex to most complex:
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cells
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tissues
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organs
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organ systems
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organism
Cells, tissues, organs and systems
Tissues
Animal cells and plant cells can form tissues, such as muscle tissue in animals. A living tissue is made from a group of cells with a similar structure and function, which all work together to do a particular job. Here are some examples of tissues:
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muscle
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the lining of the intestine
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the lining of the lungs
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xylem (tubes that carry water in a plant)
Cells, tissues, organs and systems
Organ systems
An organ system is made from a group of different organs, which all work together to do a particular job. Here are some examples of organ systems:
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circulatory system
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respiratory system
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digestive system
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nervous system
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reproductive system
the skeleton
The skeleton
Our skeleton is made of more than 200 bones. Calcium and other minerals make the bone strong but slightly flexible. Bone is a livingtissue with a blood supply. It is constantly being dissolved and formed, and it can repair itself if a bone is broken.
Function of the skeleton
The skeleton has four main functions:
- to support the body
- to protect some of the vital organs of the body
- to help the body move
- to make blood cells
the skeleton
joints
Joints
Bones are linked together by joints. Most joints allow different parts of the skeleton to move. The human skeleton has joints called synovial joints.
The synovial joint
The synovial joint
If two bones just moved against each other, they would eventually wear away. This can happen in people who have a condition called arthritis. To stop this happening, the ends of the bones in a joint are covered with a tough, smooth substance called cartilage. This is kept slippery by a liquid called synovial fluid. Tough ligaments join the two bones in the joint and stop the joint falling apart.
Muscles
Antagonistic muscles
Antagonistic muscles
Muscles can only pull and cannot push. This would be a problem if a joint were controlled by just one muscle. As soon as the muscle had contracted and pulled on a bone, that would be it, with no way to move the bone back again. This problem is solved by having muscles in pairs, calledantagonistic muscles.
For example, your elbow joint has two muscles that move your forearm up or down. These are the biceps on the front of the upper arm and the triceps on the back of the upper arm:
- to raise the forearm, the biceps contracts and the triceps relaxes
- to lower the forearm again, the triceps contracts and the biceps relaxes
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